Decoupling tool shaft from cable driven load

Abstract

The tool shaft is decoupled from the cable drive load. Providing a surgical tool including a hollow shaft and a cable extending within the shaft, the cable being isolated from an external force applied to the shaft; the shaft and the carriage are included as connecting rods of the four-bar mechanism, and the four-bar mechanism further comprises a first side connecting rod and a second side connecting rod. The first side link and the second side link are rotatably mounted to the carriage at a first distal pivot axis and a second distal pivot axis, respectively, and are rotatably mounted to the shaft at a first proximal pivot axis and a second proximal pivot axis, respectively; a length of cable extends between a distal pulley rotatably mounted at the carriage and a proximal pulley rotatably mounted at the shaft, and a length of cable extends within the shaft; the distance between the first distal pivot axis and the first proximal pivot axis matches the distance between the axis of the distal pulley and the axis of the proximal pulley such that rocking movement of the four-bar linkage due to an external force on the shaft does not exert a force on the cable.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 2019800747186 (PCT / US2019 / 061883), titled "Disconnecting a Tool Shaft from a Cable-Driven Load", filed on November 15, 2019.

[0002] Declaration of Priority

[0003] This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 767,885, filed on November 15, 2018, the entire content of which is incorporated herein by reference. Background Art

[0004] Minimally invasive medical techniques are designed to reduce the amount of damaged tissue during diagnostic or surgical procedures, thereby reducing patient recovery time, discomfort, and harmful side effects. Robotic-assisted telesurgical systems using robotic-assisted technology can be used to overcome the limitations of manual laparoscopic surgery and open surgery. Advancements in telepresence systems provide surgeons with a view inside the patient, an increased number of degrees of freedom of movement of surgical tools, and the ability to perform telesurgical procedures remotely. In manual minimally invasive surgery, the surgeon interacts with the patient via a long-shaft sensing tool, which eliminates tactile cues and masks force cues.

[0005] In a telesurgical system, since the surgeon no longer directly manipulates the tool, natural force feedback is eliminated. Instead, an end effector at the distal end of the long shaft is actuated by a control cable extending within the shaft. Sensors at the proximal portion of the shaft can be used to measure the clinical force applied to the patient tissue during a medical procedure due to contact between the end effector and the patient tissue.

[0006] Unfortunately, the force applied by the control cable extending within the shaft can be significantly greater than the clinical force generated due to contact between the end effector and the patient's contacting tissue. Therefore, there is a need to isolate the clinical force from the cable force. Brief Description of the Drawings

[0007] Aspects of the present disclosure may be best understood from the following detailed description when read in conjunction with the Figure 1 accompanying drawings. It should be emphasized that, in accordance with standard practice in the industry, the various features are not drawn to scale. In fact, for clarity, the dimensions of the various features may be arbitrarily increased or decreased. Additionally, the present disclosure may repeat reference numerals and / or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself indicate a relationship between the various embodiments and / or configurations discussed.

[0008] Figure 1 is a diagrammatic plan view of a minimally invasive telesurgical system for performing minimally invasive diagnostic or surgical procedures on a patient lying on an operating table.

[0009] Figure 2 is a perspective view of a surgeon's console.

[0010] Figure 3 is a perspective view of a manipulator unit of a minimally invasive remote operating surgical system.

[0011] Figure 4 is an illustrative side view of a surgical tool coupled to a tool carriage.

[0012] Figures 5A - 5B is an illustrative schematic diagram showing a four-bar linkage operatively coupled to a proximal portion of a tool shaft and a vertical sensor in an intermediate position ( Figure 5A ) and in an axially displaced position ( Figure 5B ), where in the intermediate position no vertical force is applied to the shaft and in the axially displaced position a vertical force is applied to the shaft.

[0013] Figure 5C is an illustrative schematic diagram showing an alternative example four-bar linkage including a differential coaxial inductive displacement sensor and a spring force sensor.

[0014] Figures 6A - 6C is an example intermediate ( Figure 6A ), lowered ( Figure 6B ) and raised ( Figure 6C ) four-bar linkage embodiment illustrative side view, where a rear chassis and a shaft assembly are coupled to act as a link.

[0015] Figure 7 is an illustrative schematic side cross-sectional view of an embodiment of the sensor of FIG. 6.

[0016] Figure 8 is an illustrative simplified top view showing the layout of a steering guide pulley, a waterfall guide pulley and a cable drive member of a four-bar linkage embodiment installed according to some embodiments to Figures 6A - 6C .

[0017] Figure 9 is showing Figure 8 an illustrative partial perspective view of the arrangement of a first set and a second set of steering guide pulleys and a first set and a second set of waterfall guide pulleys.

[0018] Figure 10 is Figures 6A - 6C an illustrative perspective view of a first embodiment of a lower second side link and a flexure beam and sensor assembly of

[0019] Figure 11 is Figures 6A - 6C an illustrative partial perspective view of a second embodiment of a lower second side link and a flexure beam and sensor assembly of

[0020] Figure 12 is Figures 6A - 6C An illustrative perspective view of a second side link below this and a third embodiment of a flexure beam and a sensor assembly. DETAILED DESCRIPTION

[0021] REMOTE OPERATING SURGICAL SYSTEM

[0022] Figure 1 is an illustrative plan view of a minimally invasive remote operating surgical system 10 for performing minimally invasive diagnostic or therapeutic surgery on a patient 12 lying on an operating table 14. The system includes a user control unit 16 for use by a surgeon 18 during the surgery. One or more assistants 20 may also participate in the surgery. The minimally invasive remote operating surgical system 10 further includes one or more manipulator units 22 and an auxiliary unit 24. When the surgeon 18 observes the surgical site through the user console 16, the manipulator unit 22 is capable of manipulating at least one surgical instrument 26 through a minimally invasive incision or a natural body orifice on the body of the patient 12. Images of the surgical site can be obtained through an endoscope 28 (such as a stereoscopic endoscope), and the manipulator unit 22 can be used to position the endoscope. A computing processor located on the auxiliary unit 24 can be used to process the images of the surgical site for subsequent display to the surgeon 18 through the user console 16. The computer processor can include a logic unit and a memory that stores instructions executed by the logic unit. In some embodiments, stereoscopic images can be captured, which allows for the perception of depth during the surgery. The number of single-use surgical instruments 26 will typically depend on the diagnostic or therapeutic procedure and the spatial constraints within the surgical site and other factors. If it is necessary to replace one or more surgical instruments 26 used during the surgery, the assistant 20 can remove the surgical instrument 26 from the manipulator unit 22 and replace it with another surgical instrument 26 on a tray 30 in the operating room. An example computer processor at the auxiliary unit 24 can be configured to process signals indicating the forces applied at the surgical instrument. The example computer processor can generate haptic feedback corresponding to these applied forces on the surgeon's console 16.

[0023] Figure 2is a perspective view of the user console 16. The surgeon's console 16 includes an observer display 31, which includes a left-eye display 32 and a right-eye display 34 for presenting a coordinated stereoscopic view of the surgical site to the surgeon 18, enabling depth perception. The user console 16 also includes one or more manual control input devices 36, 38 to receive large-scale manual control movements. One or more slave surgical instruments 26, which are mounted for use on one or more corresponding manipulator units 22, move at a relatively smaller scale distance, which matches the larger-scale manipulation by the surgeon 18 of the one or more master control inputs 36, 38. The master control input devices 36, 38 can provide the same mechanical degrees of freedom as the associated slave surgical instruments 26, providing the surgeon 18 with a sense of telepresence or that the master control input device 36 is integral with the slave surgical instrument 26, thus giving the surgeon a keen sense of directly controlling the instrument 26. For this purpose, position, force, and tactile feedback sensors (not shown) can be employed to transmit the position, force, and touch sensations from the slave surgical instrument 26 to the surgeon's hand through the control input devices 36, 38, with the surgeon's hand being subject to communication delay constraints. A signal (optionally optical or electronic), which is modulated based on the force detected at a force sensor (not shown) at the instrument 26, can be processed by a processor at the auxiliary unit cart 24 to generate a tactile feedback indicating the detected force at the control input device 36.

[0024] Figure 3 is a perspective view of the manipulator unit 22 of an exemplary minimally invasive remote operating surgical system 10 according to some embodiments. The manipulator unit 22 includes four manipulator support structures 72. Each manipulator support structure 72 includes an articulated support structure 73 pivotally mounted end-to-end and a pivotally mounted support spar 74. A corresponding slave surgical instrument carriage 75 (which includes a motor for controlling the movement of the instrument) is mounted at each support spar 74. Additionally, each manipulator support structure 72 can optionally include one or more (e.g., non-powered and / or lockable) assembly joints at the junction of the articulated support structure 73 and at the junction with the spar 74. The carriage 75 can move along the spar 74 to position the carriage 75 at different positions along the spar 74. Thus, the spar 74 can be used to position the attached slave surgical instrument carriage 75 relative to the patient 12 for surgery. Each slave surgical instrument 26 is removably attached to the carriage 75. Although the manipulator unit 22 is shown as including four manipulator support structures 72, more or fewer manipulator support structures 72 can be used. Generally, at least one of the slave surgical instruments will include a vision system, which typically includes an endoscopic camera instrument for capturing video images and one or more video displays, which are coupled to one of the carriages 75, for displaying the captured video images.

[0025] In one aspect, the carriage 75 houses a plurality of remotely operated actuators (such as motors (not shown)) that apply motion to a tension member (such as a cable drive element) that includes one or more of a drive shaft and a winch (not shown), and the tension member in turn drives cable motion that the surgical instrument 26 converts into various movements of the end effector portion of the surgical instrument 26. In some embodiments, the remotely operated actuators in the carriage 75 apply motion to various components of the surgical instrument 26, such as, for example, end effector wrist movement or jaw movement.

[0026] The surgeon manipulates the master control input devices 36, 38 to control the end effector of the instrument. Inputs (“master” commands) provided by the surgeon or other medical personnel to the control input devices 36 or 38 are converted by the surgical instrument 26 into corresponding actions (corresponding “slave” responses) by actuating one or more remote motors. A flexible cable-based force transfer mechanism or the like is used to transfer the motion of each of the remotely located remotely operated motors to the actuator output devices that dock the corresponding instruments at the instrument carriage 75. In some embodiments, the mechanical adapter interface 76 mechanically couples the instrument 26 to the actuator 443 within the instrument carriage to control the motion within the instrument 26. The surgical instrument 26 may be mechanically coupled to a first actuator (not shown) that may control a first motion of the surgical instrument, such as longitudinal (z-axis) rotation. The surgical instrument 26 may be mechanically coupled to a second actuator (not shown) that may control a second motion of the surgical instrument, such as planar two-dimensional (x, y) motion. The surgical instrument 26 may be mechanically coupled to a third actuator that may control a third motion of the surgical instrument, such as, for example, the opening and closing of the jaws of the end effector.

[0027] Figure 4Is a schematic side view of a surgical tool 26 coupled to a carriage 75. The tool 26 includes an elongated hollow cylindrical tubular shaft 410 having a distal portion 450 and a proximal portion 456. The distal portion 450 includes an end effector 454 for insertion into a patient's body cavity, and the proximal portion 456 is fixed to a proximal tool controller 440. The inner wall of the shaft defines a cylindrical hollow bore. The shaft 410 includes a longitudinal central axis 411 ("shaft central axis") between the proximal and distal portions. As used herein, the term "proximal" refers to a position on the surgical tool closer to the manipulator arm, and the term "distal" refers to a position on the surgical tool farther from the manipulator arm. The proximal tool controller 440 includes a housing 441 (shown as transparent and indicated by a dashed line), and the housing 441 encapsulates a rear chassis 442 that mounts a plurality of cable drive elements 460. The plurality of cable drive elements 460 may include, for example, one or more winches and drive shafts, which are configured to couple a driving force applied by one or more actuators 443 within the carriage 75 to a cable extending within the shaft 410 and aligned parallel to the axis 411 of the shaft. According to some embodiments, the drive member 460 is disclosed in co-pending U.S. Provisional Patent Application No. 62 / 767,895, filed November 15, 2018, the entire content of which is hereby expressly incorporated by reference. The cable 470 extends within the shaft, between the drive member 460 and the end effector 454.

[0028] The end effector 454 may include functional mechanical degrees of freedom, such as jaws that open or close, a knife that translates along a path, or a wrist 452 that can move in the x and y directions. U.S. Patent No. 6,394,998 shows an example of an end effector having multiple mechanical degrees of freedom. The distal portion 450 of the tool 26 is capable of providing any of a variety of different types of end effectors 454, such as forceps, needle drivers, cautery devices, cutting tools, imaging devices (e.g., an endoscope or an ultrasound probe), or the like.

[0029] The cable 470 is operatively coupled such that movement of the cable can apply motion to the end effector 454, for example, to open or close jaws, drive wrist movement, or operate other distal actuator components. Thus, by causing the drive member 460 within the housing 441 of the proximal tool controller 440 to apply a control force to the cable 470 extending within the shaft 410, parallel to the axis 411 of the shaft, between the drive member 460 and the end effector 454, an actuator 443 (e.g., a motor) located at the carriage 75 near the proximal portion 456 of the shaft 410 controls the movement of the end effector 454 at the distal portion 450 of the shaft 410.

[0030] Decoupling vertical clinical force from lateral cable actuation force

[0031] Figures 5A - 5B is a diagrammatic schematic view of a four-bar linkage 502 that is operably coupled to the proximal portion of the carriage 75 and the sensor 562. As Figure 5A shown, the linkage 502 is in an intermediate position where no axial force is applied to the shaft 410. As Figure 5B shown, the linkage 502 is displaced because the shaft 410 is in an axially displaced position where an axial force F H is applied to the end effector 454. It can be seen that the axial force F H is transmitted via the shaft 410 and via the linkage 502 to the sensor 562 that is coupled to the chassis 442. In this way, the axially oriented force on the end effector 454 is sensed by the sensor 562.

[0032] The sensor 562 can be configured as a deflecting sensor to measure the amount of deflection of the diaphragm area 702 (described below) of the sensor 562 caused by the axial force F H The amount of deflection represents the magnitude of the force F H In some embodiments, the sensor 562 includes a force sensor that is configured to sense a force defined between approximately ±20 N. In the absence of an axial force being applied to the housing 440 (as Figure 5A shown), the actuator 443 within the carriage 75 applies a force to the cables 550, 552 to hold the links of the four-bar linkage 502 in an intermediate position such that no force is applied to the sensor 562. In the absence of an axial force F H being applied to the end effector 454 (as Figure 5B shown), the links of the four-bar linkage are displaced to apply a linkage force F L to the sensor 562. In some embodiments, the magnitude of the linkage force F L is proportional to the magnitude of the housing force F H

[0033] ​More specifically, the four-bar linkage 502 includes an upper first side link 504, a lower second side link 506, an end third frame link 508, and an end fourth coupler link 510, all of which are joined together in a double-rocker configuration. A portion of the tool carriage 75 or alternatively another component coupled to the carriage 75 may form the frame link 508. Also, a portion of the shaft 410 or alternatively another component coupled to the shaft 410 may form the coupler link 510. In some embodiments, the four-bar linkage 502 is formed of a rigid material such as plastic, aluminum, titanium, stainless steel, or a composite material such as carbon-filled plastic. A first pivot joint 512 having a first pivot joint axis 513 pivotally couples a proximal first end portion 504p of the first side link 504 to a proximal portion of the frame link 508. A second pivot joint 514 having a second pivot joint axis 515 pivotally couples a proximal first end portion 506p of the second side link 506 to a distal portion of the frame link 508. A third pivot joint 516 having a third pivot joint axis 517 pivotally couples a distal second end portion 504d of the first side link 504 to a proximal portion of the coupler link 510. A fourth pivot joint 518 having a fourth pivot joint axis 519 pivotally couples a distal second end portion 506d of the second side link 506 to a distal portion of the coupler link 510. The frame link has a fixed position in space relative to the first link, the second link, and the fourth link, and the links move relative to the frame link as the shaft 410 translates laterally along the shaft central axis 411. The first pivot axis, the second pivot axis, the third pivot axis, and the fourth pivot axis are parallel to each other.

[0034] The first side link length of the first side link 504 between the first pivot joint axis 513 and the third pivot joint axis 517 (“side lateral length” or “S” LL ”) is equal to the second side link length of the second side link 506 between the second pivot joint axis 515 and the fourth pivot joint axis 519. In other words, the first side link 504 and the second side link 506 have matching side lateral lengths between their respective pivot joints. The first side link 504 and the second side link 506 each have respective longitudinal axes 504A, 506A. The respective longitudinal axes 504A, 506A are skewed from the axis of the shaft 411 as they are not aligned parallel to the axis of the shaft 411. The end lateral length of the frame link 508 between the first pivot joint axis 513 and the second pivot joint axis 515 (“E” LL”) is equal to the end transverse length of the coupler link 510 between the third pivot joint axis 517 and the fourth pivot joint axis 519. The frame link 508 and the coupler link 510 each have respective longitudinal axes 508A, 510A. As used herein, the term “transverse” refers to a direction parallel to the longitudinal axes 504A, 506A of the first side link 504 and the second side link 506, and the term “vertical” refers to a direction parallel to the longitudinal axes 508A, 510A of the frame link 508 and the coupler link 510.

[0035] The proximal portion of the hollow shaft 410 is fixed at the distal portion of the coupler link 510. Thus, the vertically upward and vertically downward axial movement of the hollow shaft 410 (axis 411 parallel to the shaft) causes rotational movement of the four links 504, 506, 508, 510 of the four-bar linkage 502 about the four pivot joints 512, 514, 516, 518, which results in the rocking movement of the first side link 504 and the second side link 506. More specifically, the movement applied to the coupler link 510 by the axial movement of the shaft 410 causes the first pivot joint 512 and the third pivot joint 516 to guide the corresponding movement of the distal second end portion 504d of the first side link 504 to follow the axial movement of the shaft 440. Similarly, the movement applied to the coupler link 510 by the axial movement of the shaft 440 causes the second pivot joint 514 and the fourth pivot joint 518 to guide the corresponding movement of the distal second end portion 506d of the second side link 506 to follow the axial movement of the shaft 440. Throughout this movement of the coupler link 510 and the corresponding rocking movement of the first side link 504 and the second side link 506, the longitudinal axes 504A, 506A of the first side link 504 and the second side link 506 continuously extend parallel to each other, and the longitudinal axes 508A, 510A of the frame link 508 and the coupler link 510 continuously extend parallel to each other.

[0036] The first set of distal waterfall guide pulleys 520W and the second set of distal waterfall guide pulleys 522W are rotatably mounted to the coupler link 510. The corresponding first set of proximal rear steering guide pulleys 530S and the second set of proximal rear steering guide pulleys 532S are rotatably mounted to the frame link 508. In the exemplary four-bar linkage assembly 502, the waterfall guide pulleys 520W, 522W and the steering pulleys 530S, 532S are arranged to rotate perpendicular to each other. Each waterfall pulley 520W, 522W has a waterfall pulley rotation axis 521, 523 extending parallel to the axis of the four-bar linkage pivot joint. Each steering guide pulley 530S, 532S has a steering guide pulley rotation axis 531, 533 extending perpendicular to the waterfall pulley axis and parallel to the axis 508A of the frame 508. The corresponding first set of cable drive members 540D and the second set of cable drive members 542D are rotatably mounted to the frame link 508 using rotation axes 541, 543 extending perpendicular to the waterfall pulley axes 521, 523. It will be understood that once the cable exits the four-bar linkage, other actuators can be used to drive the cable in different directions (not shown). For simplicity of the drawings and description, only one waterfall guide pulley, one steering guide pulley, and one drive member in each set are shown. It will be understood that for convenience, the term "waterfall" is used to denote the position of the distal guide pulleys at the coupler link 510 and how the cable is routed around the distal guide pulleys and into the shaft. Additionally, it will be understood that for convenience, the term "steering" is used to denote the position of the proximal guide pulleys at the frame link 508, and as described above, the cables on these proximal guide pulleys can be used for end effector actuation.

[0037] As shown, the rotational center axes 521, 523 of the first set of waterfall guide pulleys 520W and the second set of waterfall guide pulleys 522W are located at the coupler link 510 between the third pivot joint 516 and the fourth pivot joint 518. The rotational center axes 521, 523 of the first set of waterfall pulleys 520W and the second set of waterfall pulleys 522W are vertically offset from each other by a pulley vertical offset P VO . The center axis 521 of the first set of waterfall pulleys 520W is closer to the first side linkage 504 in the vertical direction compared to the center axis 523 of the second set of waterfall pulleys 522W. Similarly, the center axis 523 of the second set of waterfall pulleys 522W is closer to the second side linkage 506 in the vertical direction compared to the center axis 521 of the first set of waterfall pulleys 520W.

[0038] Also as shown, the rotational center axes 521, 523 of the first set of waterfall pulleys 520W and the second set of waterfall pulleys 522W are laterally offset from each other by a pulley lateral offset P LO . This offset PLO It is also shown that, compared to the axis of rotation 523 of the second set of cascading pulleys 522W, the axis of rotation 521 of the first set of cascading pulleys 520W is laterally further away from the central axes 513, 515 of the first pivot joint 512 and the second pivot joint 514. Compared to the central axis 521 of the first set of cascading pulleys 520W, the central axis 523 of the second set of cascading pulleys 522W is laterally disposed closer to the central axes 513, 515 of the first pivot joint 512 and the second pivot joint 514 by a pulley lateral deviation amount P. LO It should be understood that the deviation amount P of the cables guided around the first set of cascading pulleys 520W and the second set of cascading pulleys 522W LO allows the cables 550, 552 guided by these pulleys to be positioned to extend within the shaft 410 and be laterally spaced apart from each other parallel to the central axis 411 of the shaft.

[0039] The first set of rear turning guide pulleys 530S and the second set of rear turning guide pulleys 532S are mounted to the frame link 508 at positions vertically offset from each other by a pulley vertical deviation amount P VO The central axis 531 of the first set of turning pulleys 530S at the frame link 508 is closer to the first side link mechanism 504 in the vertical direction compared to the central axis 533 of the second set of turning pulleys 532S. The central axis 533 of the second set of turning pulleys 532S is disposed at the frame link 508 and is closer to the second side link mechanism 506 in the vertical direction compared to the central axis 531 of the first set of turning pulleys 530S. The central axes 531, 533 of the first set of turning pulleys 530S and the second set of turning pulleys 532S are laterally offset from each other at the frame link 508 by a pulley lateral deviation amount P LO Compared to the central axis 533 of the second set of turning pulleys 532S, the central axis 531 of the first set of turning pulleys 530S is laterally disposed closer to the central axes 517, 519 of the third pivot joint 516 and the fourth pivot joint 518. Compared to the central axis 531 of the first set of turning pulleys 530S, the central axis 533 of the second set of turning pulleys 532S is laterally disposed further away from the central axes 517, 519 of the third pivot joint 516 and the fourth pivot joint 518.

[0040] Multiple cables 550, 552 extend parallel to the axis 411 of the shaft within the hollow shaft 410. Each of the cables 550, 552 is anchored at its proximal end to a respective cable drive member 540D, 542D and at its distal end to the end effector 454. Each of the cables 550, 552 engages a respective deflection pulley 530S, 532S and a respective waterfall pulley 520W, 522W. In some embodiments, for example, the cables are formed of a material such as stainless steel, titanium, or tungsten or a synthetic material such as polyethylene or polybenzoxazole (PBO). More specifically, each cable 550S, 552S includes a cable portion wound around the peripheral engagement surface of its associated deflection pulley 530S, 532S, and each cable is wound around the circumferential engagement surface of its associated waterfall pulley 520W, 522W at the coupling link 510. Thus, each cable 550S, 552S extends respectively between the respective axes 531, 533 of its associated deflection pulley 530S, 532S and the respective axes 521, 523 of its associated waterfall pulley 520W, 522W. For simplicity of the drawings and description, only two cables 550, 552 are shown, but in some embodiments, four, six, or more than six cables may be used.

[0041] The first set of waterfall pulleys 520W and the second set of waterfall pulleys 522W, as well as the first set of turning pulleys 530S and the second set of turning pulleys 532S, are configured to keep each of the plurality of cables 550, 552 aligned parallel to the first side link 504 and the second side link 506 both when the four-bar linkage is at rest in the middle position and when the four-bar linkage is displaced during its rocking motion. According to some embodiments, the first cable 550 and the second cable 552 are pre-tensioned with a force of 0.5 - 5 lbf. The intermediate cable section of the first cable 550 has a length that matches the lateral length of the side and is between the central axis 521 of the first set of waterfall pulleys 520W and the central axis 531 of the first set of turning pulleys 530S. Similarly, the intermediate cable section of the second cable 552 has a length that matches the lateral length of the side and is between the central axis 523 of the second set of waterfall pulleys 522W and the central axis 533 of the second set of turning pulleys 532S. The first set of turning pulleys 530S and the second set of turning pulleys 532S are rotatably mounted at positions at the frame link 508, and the first set of waterfall pulleys 520W and the second set of waterfall pulleys 522W are rotatably mounted at positions at the coupling link 510 such that when the four-bar linkage 502 is at rest and when the four-bar linkage 502 undergoes a rocking motion as the shaft 410 moves vertically, these turning pulleys and waterfall pulleys guide the intermediate cable sections of the first cable 550 and the second cable 552 to extend parallel to the first side link 504 and the second side link 506. Thus, for example, even during the rocking of the first side link 504 and the second side link 506 in response to the vertical movement of the shaft 440, the intermediate cable sections of the first cable 550 and the second cable 552 continuously extend parallel to the first side link 504 and the second side link 506.

[0042] The flexure beam 560 includes a distal first end portion 560d and a proximal second end portion 560p. The distal first end portion 560d of the flexure beam is coupled to the proximal first end portion 506p of the second side link 506. The proximal second end portion 560p of the flexure beam is operatively coupled to the sensor 562. More specifically, the flexure beam 560 is operatively coupled to apply a L force to the sensor 562, the magnitude of which is proportional to the axial force F H applied by the shaft housing 440 to the coupling link 510 during the axial movement of the shaft 440. Specifically, by way of example, F HAnd its associated vertical displacement is transmitted from the end effector to the coupler link via the shaft. The magnitude of the link force applied to the sensor 562 due to the corresponding force exerted by the shaft on the coupler link 510 is determined based on the length of the flexure beam 560. During the rocking motion of the four-bar linkage 502, the rotation of the distal first end portion 506d of the second side link 506 about the second pivot joint axis 515 (which is caused by the force applied to the coupler link 510 due to the axial motion of the shaft 440) causes a corresponding motion of the flexure beam 560, which in turn applies a corresponding link force F L to the sensor, which force is proportional to the axial force F H applied by the shaft 440 to the coupler link 410.

[0043] In some embodiments, the flexure beam 560 is optionally formed of a material such as aluminum, stainless steel, or titanium, or it is optionally formed of a composite material such as carbon-filled plastic. The flexure beam 560 is configured to have a bending stiffness that is less than the bending stiffness of the linkages of the four-bar linkage 502 in a direction parallel to the central axis 411 of the shaft 410. The linkages of the four-bar linkage 502 have a sufficiently high bending stiffness such that they do not bend in response to the cable forces applied by the cable drive members 540D, 542D. Similarly, the links of the four-bar linkage 502 have a sufficiently high bending stiffness such that they do not bend during normal rocking motion in response to the axial motion of the shaft 410. The insertion stiffness of the instrument shaft 410 is in the range of 5 - 50 N / mm. In some embodiments, the total cable force can be in the range of about 100 lbf. In contrast, the bending stiffness of the flexure beam 560 is small enough to flex during normal rocking motion of the four-bar linkage 502 in response to the axial motion of the shaft 410. More specifically, in some embodiments, the flexure beam 560 has a sufficiently low bending stiffness to flexibly bend in response to certain axial forces applied to the coupler link 510 during axial motion of the shaft 410 without suffering damage such as fracture. In some embodiments, for example, the axial force is caused by an axial clinical force that is applied to the end effector 454 at the distal portion of the shaft 410 due to the end effector contacting anatomical tissue. In some embodiments, such a clinical force can be in the range of about 20 N.

[0044] The waterfall pulleys 520W, 522W and the steering pulleys 530S, 532S are configured to always (including throughout the rocking motion of the four-bar linkage 502) maintain the middle cable segment in parallel alignment with the longitudinal axes 504A, 506A of the first side link mechanism 504 and the second side link mechanism 506, decoupling the cable force at the four-bar linkage 502 from the force applied at the four-bar linkage 502 due to the motion of the shaft 410. A larger cable force is applied to the middle cable segment in a direction parallel to the longitudinal axes 504A, 506A of the first side link 504 and the second side link 506. A much smaller clinical force applied to the shaft can be applied to the coupler link 510 in a direction perpendicular to the longitudinal axes 504A, 506A of the first side link 504 and the second side link 506. Thus, the cable forces F C1 , F C2 acting on the cables 550, 552 that drive the end effector 454 and are applied to the four-bar linkage 502 are isolated from the axial force F H applied to the four-bar linkage 502 due to the axial motion of the shaft 410. Thus, a smaller contact force at the end effector 454 applies a corresponding vertical force F H to the shaft 410 and the coupler link 510, and this vertical force is isolated from the larger lateral cable forces F C1 , F C2 applied to the cables 550, 552. The vertical (axial) force F H causes the rocking motion of the four-bar linkage 502 and the flexible beam 560 coupled thereto, which in turn applies a link force F L to the sensor 560, the magnitude of which is proportional to the smaller vertical (axial) force F H .

[0045] Figure 5CFIG. is a schematic diagram illustrating an alternative exemplary four-bar linkage including a differential coaxial coil inductive displacement sensor 552 and a spring force sensor 554. In various embodiments, the dual-coil distance displacement force sensor 552 may be used in combination with a flexure 554 to measure the axial force applied to the instrument shaft 410. The axial direction is considered to be the direction parallel to the central axis 411. Exemplary displacement sensor 552 includes a sensor shaft 558, a proximal toroidal coil 560, and a distal toroidal coil 562. The proximal and distal coils are located in fixed positions and are coaxially aligned with the sensor shaft 558. The sensor shaft 558, as well as the proximal coil 560 and the distal coil 562, are arranged to allow the sensor shaft 558 to move axially when inserted into the coils 560, 562. A magnetic material structure 566 is located on the sensor shaft 558, and the sensor shaft 558 is fixed to the tool shaft 410 such that the tool shaft 410 and the sensor shaft 558 move axially in unison. An axial direction force that causes axial displacement of the tool shaft 410 applied to the end effector 454 at the distal end of the tool shaft 410 results in a corresponding axial force acting on the sensor shaft 558 and displacement of the sensor shaft 558.

[0046] When “at rest,” with no axial direction force applied to the tool shaft 410, the sensor shaft 558 may be axially positioned such that the magnetic material structure 566 is partially located within each of the toroidal proximal coil 560 and the toroidal distal coil 562. With no axial direction force applied to the tool shaft 410, equal portions of the magnetic material structure 566 may be located within each of the coils 560, 562. Each coil may be coupled into an independent LC circuit (not shown), where the coil serves as an inductor (L) and where the inductance varies with the amount of magnetic material contained within the corresponding coil. The resonant frequency of each circuit varies with the change in the inductance of the corresponding circuit.

[0047] When an axial force causes axial movement of the tool shaft 410 and the sensor shaft 558, the proportion of the magnetic material structure 566 within each of the proximal coil 560 and the distal coil 560 changes. The inductance of one of the coils increases while the inductance of the other decreases. As a result, the proximal coil 560 and the distal coil 562 have mismatched inductance values. The independent LC circuits are used to measure the inductance difference of the coils, which provides an indication of the axial displacement distance of the sensor shaft 558.

[0048] The flexure member 554 has a portion fixed to the proximal part of the lower second side link 506 and has an opposite end fixed to the frame link 508. The flexure member 554 has a known stiffness that can be used to apply a force based on the displacement of the flexure member. The displacement measurement of the sensor shaft 558 based on the measurement results of the inductance values of the proximal coil 560 and the distal coil 562 is used to determine the sensor shaft displacement distance. The inductive coils 560, 562 can be used to measure the shaft displacement. The flexure member 554 can be used to measure the corresponding axial force; the flexure member has a known stiffness, and the amount of flexure member displacement represents the magnitude of the axial force applied to the end effector and transmitted by the side link 506 to the flexure member 554. Thus, the shaft displacement can be calibrated to the flexure member displacement, and the flexure member stiffness can be used to determine the axial force corresponding to the shaft displacement. An example of force measurement using a differential coaxial inductive displacement sensor used with a spring force sensor is provided in U.S. Patent Application No. 62 / 901,729, filed on September 17, 2019, the entire content of which is hereby expressly incorporated by reference.

[0049] Figures 6A - 6C is a diagrammatic side view of an embodiment of the four-bar linkage 602, in which the rear chassis 442 and the shaft assembly 601 are coupled to serve as the frame link and the coupler link, respectively. As described above, the proximal tool controller 440 includes the rear chassis 442. Figure 6A Shows the four-bar linkage 602 in an intermediate position, in which the upper side bar 604 and the lower side bar 606 are horizontally aligned. Figure 6B Shows that when the shaft 410 is set in the axially lower position, the upper side bar 604 and the lower side bar 606 rotate slightly downward. Figure 6C Shows that when the shaft is set in the axially vertically higher position, the upper side bar 604 and the lower side bar 606 rotate slightly upward.

[0050] The four-bar linkage includes an upper first link 604, a lower second side link 606, a frame link 608, and a coupler link 610. The rear chassis 442 serves as the frame link 608. The shaft assembly 601 serves as the coupler link 610. The waterfall pulley and the steering pulley are omitted to simplify the drawing and avoid hiding the details of the four-bar linkage 602.

[0051] The proximal part of the upper first side link 604 is rotatably coupled to the frame link 608 at the first pivot joint 612. The proximal part of the lower second side link 506 is rotatably coupled to the frame link 608 at the second pivot joint 614. The distal part of the upper first side link 604 is rotatably coupled to the frame link 610 at the third pivot joint 616. The distal part of the lower second side link 606 is rotatably coupled to the frame link 610 at the fourth pivot joint 616. Along the lateral length of the upper first side link between the first pivot joint and the third pivot joint (SLL ) is equal to the lateral length along the lower second side link between the second pivot joint and the fourth pivot joint. The end lateral length (E) of the frame link 608 between the first pivot joint 612 and the second pivot joint 614 LL ) is equal to the end lateral length (E) of the coupler link 610 between the third pivot joint 616 and the fourth pivot joint 618 LL ).

[0052] The first waterfall pulley mount 626 and the second waterfall pulley mount 628 are provided at the coupler link 610 to mount first and second sets of waterfall pulleys (not shown) about first and second waterfall pulley axes extending about an axis of rotation parallel to the first through fourth pivot joints 612 - 618. The first waterfall pulley mount 626 and the second waterfall pulley mount 628 are laterally offset from each other by a pulley lateral offset amount P LO . The first waterfall pulley mount 626 and the second waterfall pulley mount 628 are vertically offset from each other by a pulley vertical offset amount P VO .

[0053] The flexure beam 660 is fixedly secured to rotate about the second pivot joint 614 in unison with the second side link 606. More specifically, the distal portion 660d of the flexure beam is coupled to the distal portion of the lower second side link 606, while the proximal portion is operatively coupled to the sensor 662. Upward movement of the shaft assembly in the direction of arrow "U" causes downward movement of the proximal portion 660p of the flexure beam 660 in the direction of arrow "D". For simplicity of the drawing, the flexure beam and the sensor are not shown in Figures 6B - 6C .

[0054] Figure 7 is Figures 6A - 6C a diagrammatic side cross-sectional view of an embodiment of the sensor 662. In some embodiments, the sensor is a diaphragm force sensor that includes a thin annular substantially planar diaphragm 702 and an upright sensor beam 704 arranged to apply a perpendicular force to the diaphragm 702. The diaphragm 702 includes a first surface 706 and a second surface 708 of reverse-facing planes. A strain gauge 710 is disposed on the second surface 708. The proximal portion 660p of the flexure beam 660 is operatively coupled to apply a perpendicular link force F to the upright sensor beam 704 in response to rotation of the lower second side link 606 about the second pivot joint 614 L . In some embodiments, the first surface 706 of the diaphragm 702 may have a wavy profile to increase force measurement sensitivity. A diaphragm sensor having a diaphragm surface with a wavy profile is disclosed in U.S. Patent Application No. 62 / 767,891, filed Nov. 15, 2018, the entire content of which is expressly incorporated herein by reference.

[0055] Figure 8 is a simplified top view illustration showing the layout of the steering guide pulleys 730S, 732S, waterfall guide pulleys 720W, 7222W, and cable drive element 850 of a four-bar linkage embodiment mounted to Figures 6A - 6C . Various details are omitted or simplified so as not to obscure the pulley layout. The first set of steering pulleys 730S and the second set of steering pulleys 732S are rotatably mounted to the chassis 442 which acts as a frame link 608. The first set of waterfall pulleys 720W and the second set of waterfall pulleys 722W are mounted to a shaft assembly (not shown) which acts as a coupler link 610. In some embodiments, the cable drive element 850 may include a winch mounted to the chassis 442 which acts as the cable drive element 850. The axes of rotation of the first set of steering pulleys 730A and the second set of steering pulleys 732A are laterally offset and perpendicular to the axes of rotation of the first set of waterfall pulleys 720W and the second set of waterfall pulleys 722W. The lateral offset between the axis of rotation of the first set of steering pulleys 730S and the axis of rotation of the first set of waterfall pulleys 720W is the lateral side length (S LL ) between the first pivot joint 612 and the third pivot joint 616. The axis of rotation of the second set of steering pulleys 732S and the axis of rotation of the second set of waterfall pulleys 722W is the lateral side length (S LL ) between the second pivot joint 614 and the fourth pivot joint 618. Thus, the axes of rotation are offset by S LL matching. The first set of steering pulleys 730S and the second set of steering pulleys 732S of the illustration each have some pulleys of different diameters, but each steering pulley is offset from its corresponding set of waterfall pulleys by the lateral side length (S LL ). It will be understood that the first set of waterfall pulleys 720W and the second set of waterfall pulleys 722W also each have some pulleys of different diameters. The smaller diameter steering pulleys are paired with the larger diameter waterfall pulleys and vice versa such that the cable lengths for all steering / waterfall pulley pairs are the same. It should be understood that using pulleys of different diameters more easily allows the cables 852 to be distributed at different positions within the shaft 410. The different diameter pulleys also allow the cables to be routed to the correct winches while keeping the cables parallel to the linkages 504 and 506. Each of the cables 852 is fixed to an associated winch and is guided by the respective steering pulley and the respective associated waterfall pulley, and the pulleys guide each of the cables 852 to be aligned with the longitudinal axis 411 of the shaft 410.

[0056] Figure 9 is a partial perspective view illustration showing Figure 8The arrangement of the first set of steering guide pulleys 730S and the second set of steering guide pulleys 732S, as well as the first set of waterfall guide pulleys 720W and the second set of waterfall guide pulleys 722W. The axes of rotation of the steering pulleys 730S, 732S are perpendicular to the axes of rotation of the waterfall pulleys 720W, 722W. The steering pulleys 730S, 732S are used to guide a cable 852 operatively coupled to a drive element (not shown) to the associated waterfall pulleys 720W, 722W, which guide the cable 852 into axial alignment with a shaft (not shown).

[0057] Figure 10 is Figures 6A - 6C An illustrative perspective view of a first embodiment of a lower second side link 606 and a flexure beam 660 and sensor 662 assembly. The distal portion 606d of the side link 606 includes a distal fork 1010 having an inward-facing pivot joint pin 1011 for pivotally mounting a shaft (not shown). The proximal portion 606p of the side link 606 includes a proximal fork 1012 having an outward-facing pivot joint pin 1013 for rotatably mounting at the second pivot joint 614 described above. The flexure beam 660 includes a first rigid arm 1020 and a second rigid arm 1022, each arm having a distal end coupled to a different one of the arms in the distal fork 1012. The flexure beam 660 includes a cross beam 1024 integrally fixed to the respective proximal ends of the first arm 1020 and the second arm 1022. The first arm 1020 and the second arm 1022 have a rectangular cross section. The cross beam 1024 is operatively coupled to a fixed upright sensor beam 704. In some embodiments, the axial stiffness along the axis of the upright sensor beam 704 is determined based on the bending stiffness of the flexure beam 660, the stiffness of the sensor diaphragm 702, and the length of the flexure beam 660. In some embodiments, the flexure beam 660 and the diaphragm 702 can be configured to provide axial stiffness along the axis of the upright beam 704 such that the effective stiffness of the instrument along the axis 411 is adjusted in such a way that it improves the stability of the remote operation of the instrument in the presence of force feedback. For those skilled in the art of designing systems for remote operation with force feedback and controls, the effect of the effective stiffness of the end effector on system stability will be apparent when interacting with the environment. This configuration provides the ability to adjust the stiffness along the axis 411 without compromising the ability to decouple the cable force from the force F applied to the end effector 454 H from being decoupled.

[0058] Figure 11 is Figures 6A - 6CAn illustrative partial perspective view of a second embodiment of the lower second side link 606 and the flexure beam 660 and sensor 662 assembly. The flexure beam has a planar profile and is mounted such that the plane of the flexure beam passes through the second pivot joint axis 515. The flexure beam has a transverse axis 1015 collinear with the second pivot joint axis and has a longitudinal axis (not shown) that aligns with the second side link longitudinal axis 506A when the flexure beam is in the rest position such that when the vertical movement of the proximal tool controller 440 causes a minimal left - right deflection of the column 704. The diaphragm sensor 662 is designed to measure the deflection of the 704 in the vertical direction, and thus it is advantageous to minimize the left - right deflection of the 704 in terms of the magnitude of the lateral deflection / load that the diaphragm sensor must reject. This embodiment shows an alternative way to achieve this alignment and reduce the complexity of parts and manufacturability.

[0059] Figure 12 is Figures 6A - 6C An illustrative perspective view of a third embodiment of the lower second side link 606 and the flexure beam 660 and sensor 662 assembly. The first rigid arm 1020 and the second rigid arm 1022 have a circular cross - section. The third embodiment has the same advantages as the second embodiment described above.

[0060] The foregoing description is presented to enable any person skilled in the art to make and use a surgical tool having a shaft that has a proximal portion suspended from a tool controller and has an end effector fixed to its distal portion. The shaft is pivotally fixed at the tool controller to a four - link mechanism structure to direct the cable force applied to a cable extending within the shaft between the tool controller and the end effector while decoupling the cable force from the clinical axial force applied to the shaft due to contact between the shaft and anatomical tissue. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the scope of the invention.

[0061] From the description herein, it can be seen that any mechanical device that performs the four - link mechanism function can replace the four - link mechanism. For example, a single rocking link that resists the cable force between the chassis and the shaft can be used, provided that the shaft is constrained to move along the shaft central axis and provided that the cable length does not change as the shaft moves relative to the tool chassis.

[0062] Moreover, from the description herein, it can be seen that other alternative spring arrangements can be used to provide the necessary vertical elastic force along the shaft central axis 411 on the shaft 410 in the proximal direction, the distal direction, or in both the proximal and distal directions. For example, one or more springs can be directly coupled to the shaft such that the shaft is held in an intermediate position and the desired proximal, distal, or proximal and distal elastic forces are applied to the shaft.

[0063] Furthermore, as can be seen from the description herein, the force sensor can be in various positions relative to the side link of the four-bar linkage (or its equivalent). For example, as described herein, the bottom side link and the force sensor beam act together as a first-class lever, but in alternative embodiments, they can be positioned as a second-class lever. Moreover, in other alternative embodiments, the force sensor beam can be coupled to the top side link of the four-bar linkage.

[0064] Furthermore, as can be seen from the description herein, the cable can optionally be driven by a drive input other than a winch. For example, an optional linear drive member can be coupled to the proximal end of the cable, and such a linear drive member can be driven by a lead screw or directly engaged with a corresponding linear actuator.

[0065] In the foregoing description, numerous details have been set forth for purposes of explanation. However, one of ordinary skill in the art will recognize that embodiments of the present disclosure may be practiced without the use of these specific details. In other instances, well-known processes are shown in block diagram form in order not to obscure the description of the invention with unnecessary detail. The same reference numerals may be used to denote different views of the same or similar elements in different figures. Thus, the foregoing description and drawings of embodiments in accordance with the present invention are illustrative only of the principles of the invention. Accordingly, it will be understood that various modifications can be made by those skilled in the art without departing from the scope of the invention as defined by the appended claims.

Claims

1. A surgical tool, which comprises: a chassis; a hollow shaft, which includes a proximal portion and a distal portion and has a longitudinal axis central axis extending between the proximal portion and the distal portion; an end effector, which is coupled to the distal portion of the shaft; a four-bar linkage mechanism, which includes the chassis, the proximal portion of the shaft, a first side link pivotally coupled to the chassis and pivotally coupled to the proximal portion of the shaft, and a second side link pivotally coupled to the chassis and the proximal portion of the shaft; a first cable drive element, which is mounted to the chassis; a first distal pulley, which is rotatably mounted to the chassis; a first proximal pulley, which is rotatably mounted to the proximal portion of the shaft; a first cable, which includes a proximal portion fixed to the first cable drive element, includes a distal portion extending within the shaft parallel to the axis central axis, and includes an intermediate section engaging the first distal pulley and engaging the first proximal pulley; wherein, the first distal pulley and the first proximal pulley are positioned to transmit the first cable between the first drive member and the proximal portion of the shaft, while isolating the cable force applied to the first cable from the axial force applied to the end effector in a direction parallel to the axis central axis.

2. The surgical tool according to claim 1, which further comprises: a second cable drive element, which is mounted to the chassis; a second distal pulley, which is rotatably mounted to the chassis; a second proximal pulley, which is rotatably mounted to the proximal portion of the shaft; a second cable, which includes a proximal portion operatively coupled to the second cable drive element, includes a distal portion extending within the shaft parallel to the axis central axis, and includes an intermediate section engaging the second distal pulley and engaging the second proximal pulley; wherein, the second distal pulley and the second proximal pulley are positioned to transmit the second cable between the second drive member and the proximal portion of the shaft, while isolating the cable force applied to the second cable from the axial force applied to the end effector in a direction parallel to the axis central axis.

3. The surgical tool according to claim 1, wherein, the first distal pulley rotation axis extends perpendicular to the first proximal pulley rotation axis.

4. The surgical tool according to claim 1, which comprises: wherein, the proximal portion of the first side link is rotatably coupled to the chassis at a first distal pivot axis, and the distal portion of the first link is rotatably coupled to the proximal portion of the shaft at a first proximal pivot axis; wherein, the first distal pulley is rotatably mounted to the chassis at a first distal pulley rotation axis; wherein, the first proximal pulley is rotatably mounted to the proximal portion of the shaft at a first proximal pulley rotation axis; wherein, the distance between the first proximal pivot axis and the first distal pivot axis matches the distance between the first distal pulley rotation axis and the first proximal pulley rotation axis.

5. The surgical tool according to claim 4, further comprising: wherein, a proximal portion of the second side link is rotatably coupled to the chassis at a second proximal pivot axis, and a distal portion of the second link is rotatably coupled to the proximal portion of the shaft at a second distal pivot axis; it further comprises: a second cable drive element mounted to the chassis; a second distal pulley rotatably mounted to the chassis at a second distal pulley rotation axis; a second proximal pulley rotatably mounted to the proximal portion of the shaft at a second proximal pulley rotation axis; wherein a distance between the second proximal pivot axis and the second distal pivot axis matches a distance between the second distal pulley rotation axis and the second proximal pulley rotation axis; further comprising: a second cable including a proximal portion fixed to the second cable drive element, including a distal portion extending within the shaft parallel to the central axis of the shaft, and including an intermediate section engaging the second distal pulley and engaging the second proximal pulley; wherein the second distal pulley and the second proximal pulley are positioned to transmit the second cable between the second drive member and the proximal portion of the shaft while isolating a cable force applied to the second cable from an axial force applied to the end effector in a direction parallel to the central axis of the shaft.

6. The surgical tool according to claim 1, further comprising: an actuator operably coupled to the first cable drive element, the actuator being configured to apply a force to the first cable to push a distal portion of the first cable in a first direction; and a second actuator operably coupled to the second cable drive element, the actuator being configured to apply a force to the second cable to push a distal portion of the second cable in a second direction opposite to the first direction.

7. The surgical tool according to claim 1, further comprising: a force sensor configured to measure a force applied to the shaft.

8. A surgical tool, which comprises: a four-bar linkage mechanism including a first side link, a second side link, a frame link, and a coupler link, wherein the first side link is rotatably coupled to the frame link and the coupler link at a first pivot joint and a third pivot joint, respectively, and the second side link is rotatably coupled to the frame link and the coupler link at a second pivot joint and a fourth pivot joint, respectively, wherein a lateral offset length between the first pivot joint and the third pivot joint matches a lateral offset length between the second pivot joint and the fourth pivot joint; a hollow shaft having a longitudinal axis, a proximal portion, and a distal portion; wherein the coupler link includes the proximal portion of the shaft; an end effector coupled to the distal portion of the shaft; a sensor; a flexure beam including a distal portion fixed to the proximal portion of the second side link and including a proximal portion operably coupled to the sensor; A first proximal guide pulley rotatably mounted to the frame link; A first distal guide pulley rotatably mounted to the coupler link; A first cable drive member mounted to the frame link; A first cable including a proximal portion fixed to the first drive member, and including a distal portion fixed to the end effector, and including an intermediate section engaging the first proximal guide pulley and the first distal guide pulley; Wherein the first proximal pulley and the first distal pulley are arranged to cooperatively guide the intermediate section of the first cable parallel to the first side link and the second side link during the rocking motion of the four-bar linkage.

9. The surgical tool according to claim 8, Wherein, The axis of rotation of the first distal guide pulley is laterally offset from the axis of rotation of the first proximal guide pulley by the lateral offset length.

10. The surgical tool according to claim 9, Wherein, The first proximal guide pulley is rotatably mounted to the frame link between the first side link and the second side link; Wherein the first distal guide pulley is rotatably mounted to the coupler link between the first side link and the second side link; It further includes: A second proximal guide pulley rotatably mounted to the frame link between the first side link and the second side link; A second distal guide pulley rotatably mounted to the coupling link between the first side link and the second side link; Wherein the axes of rotation of the first proximal guide pulley and the second proximal guide pulley are offset from each other by a pulley lateral offset amount; Wherein the axes of rotation of the first proximal guide pulley and the second proximal guide pulley are offset from each other by a pulley vertical offset amount; Wherein the axes of rotation of the first distal guide pulley and the second distal guide pulley are offset from each other by the pulley lateral offset amount; Wherein the axes of rotation of the first distal guide pulley and the second distal guide pulley are offset from each other by the pulley vertical offset amount; Wherein the axis of rotation of the first distal guide pulley is laterally offset from the axis of rotation of the first proximal guide pulley by the lateral offset length; Wherein the axis of rotation of the second distal guide pulley is laterally offset from the axis of rotation of the second proximal guide pulley by the lateral offset length; It further includes: A second cable positioned to engage the guide surface of the second proximal guide pulley, and positioned to engage the guide surface of the second distal guide pulley and axially extend within the shaft parallel to the shaft longitudinal axis; Wherein the second proximal pulley and the second distal pulley are positioned to cooperatively guide the intermediate section of the second cable parallel to the first side link and the second side link during the rocking motion of the four-bar linkage.

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